Electric switch



Nov. 24, 1953 w, l.. BusH ETAL ELECTRIC SWITCH 3 Sheets-Sheet l Filed Nov. 7, 1951 Nov. 24, 1953 w. BUSH ETAL ELECTRIC SWITCH 3 Sheets-Sheet 2 Filed Nov. 7. 1951 4 fwn/Kw WZZkJE L .Eush Arthur' M ffy Nov. 24, 1

Filed NOVa 7l 1951 w' L' BUSH ETAL ELECTRIC SWITCH 3 Sheets-SME,c 5

Patented Nov. 24, 19513 ELECTRIC SWITCH Wilkie L.`Bush and Arthur M. Daily, Elkhart, Ind., assignors to Chicago Telephone Supply Corporation, Elkhart,

Ind., a corporation of Indiana Application November 7, 1951, Serial No. 255,270

(Cl. G-77) 14 Claims.

This invention relates to electric switches and refers more particularly to switches of the type used in radio and television apparatus and generally mounted on the back of a variable resistor to be actuated by the rotatable control shaft of the resistor.

One of the main requisites of such switches is that they must be compact since the space allotted thereto in radio and television apparatus is often extremely limited.

1t is, of course, also well recognized that to meet underwriters requirements such switches must provide a positive contact when the switch is closed as well as a safe separation between contacts when the switch is open. This requirement is especially applicable to automobile radio receivers since in this case the switch must handle relatively high current. Another very important desideratum is that the actuation of such switches from one position to the other should be produced from a minimum angular motion of the rotary control shaft so as to leave practically the entire range of actuator motion for adjustment of the variable resistor.

These objectives, in a broad sense, are attained by the switch shown and claimed in the cepending application of Adrian J. Vaksvik, Serial No. 264,329, filed January 4, 1951, so that this invention is closely related to said application, especially as to the manner in which the contacts are arranged; but the manner in which the movable contacts are driven is based upon an entirely diiferent principle in this invention. Thus, the present invention is characterized by a sliding pitman. constrained to axial movement across and parallel to the base of the switch and drivingly connected to the movable contact carrier. A spring acting upon this sliding pitman yieldingly urges it and the movable contact carrier in one direction., preferably the switch closing direction, and a novel driving connection between the rotatable actuator oi he switch or variable resistor, if the switch is used in conjunction with one, translates a small angular movement of the actuator into full retraction of the pitman and movable contact carrier.

Switches of the type here under consideration are sometimes of the single pole, single throw type and sometimes of the double pole, single throw type and it is another purpose of this invention to provide an actuating mechanism for a switch of this character which is readily adaptable to either the single pole or double pole type but is especially well suited to the latter.

Another desirable attribute of all such switches as here under consideration is that they open and close at least with an indication of a snap action so that the operator clearly recognizes the opening and closing of the switch. Another object of this invention thus is to provide a simple manner of creating the impression of a snap action.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination andv arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise einbodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate two complete examples of the physical embodiment of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure l is a viewpartially in side elevation and partially in section through a combined switch and variable resistor embodying this invention;

Figure 2 is a cross sectional view through Figure l on the plane oi the line 2 2, the switch being open in this figure as it is in Figure l;

Figure 3 is a view similar to Figure 2 but showing the switch closed;

Figure 4 is a perspective view of the essential elements of the switch actuating mechanism with the driver swung out of its operative position to better illustrate the relationship between the parts;

Figure 5 is a cross sectional view through Figure l on the plane of the line 5-5;

Figure 6 is a fragmentary View illustrating particularly the connection between the rotary driver and the linearly movable pitman through which a small degree of rotation of the actuator imparts a relatively large switch opening movement to the linearly movable contact carrier;

Figure '7, like Figure 1, is a view partially in side elevation and partially in section through a combined switch and variable resistor but illustrating a slightly modified embodiment of the invention;

Figure 8 is a cross sectional View through Figure 7 on the plane of the line 8 3 and with the switch shown open as it is in Figure 7 and Figure 9 is a View similar to Figure 8 but showing the switch closed.

Referring now particularly to the accompanying drawings in which like numerals have been applied to like parts throughout the several views, and especially to that form of the invention illustrated in Figures l to 6, inclusive, the numeral 'l designates the base of the switch which, as is customary, is formed of insulating material and closes one end of a cylindrical stamped metal shell 8 to which it is secured by being conned between indentations 9 and an inturned iiange I0.

Mounted upon the base l are the stationary contacts Il of the switch and since the switch depicted is of the double pole single throw type there are four such stationary contacts arranged l in two pairs with one pair at each side of a median plane passing through the axis ofthe switch and coinciding with the longitudinal axis of a sliding driving member or pitman I2. This pitman is constrained to linear movement across and parallel to the inner face of the base 'I by having its opposite end portions slidably received in diametrically opposite holes I3 and Ill in the side wall of the cylindrical shell 8, the hole I4 being in the bottom of an indented portion I5 which enters a notch I6 in the base to properly orient the pitman with the stationary contacts on the base.

The stationary contacts II, as is generally the practice, have terminals I1 formed integrally therewith and protruding through the base. Conventional means anchor the combined terminal and contact members to the base, but since this detail forms no part of the invention it has not been illustrated.

As is no doubt Well understood, each pair of stationary contacts is arranged to be bridged by a movable contact I8, and to assure good switch closure the facing surfaces of the stationary contacts are disposed at a slight angle to one another as shown so that the movable contacts engage the stationary contacts with a wedging action.

`The movable contacts I8 are drivingly connected to a Contact carrier I9 in a manner allowing the contacts I8 to have a degree of free movement with respect to the carrier I9. The carrier, which is stamped from a sheet of insulating material, is confined between the pitman and guide edges 29 on the contacts II so that the carrier is constrained to edgewise movement in a plane parallel to the base. Each of the movable contacts I8 is a stamping having a roughly cylindrical medial portion 2l of a size to have wedging engagement between its respective pair of stationary contacts; and one end of each movable contact has a substantially T-shaped head r22 bent up therefrom and engaged in a rectangular opening 23 in the contact carrier. The other end of each movable contact has a lug 24 struck up therefrom and received in a correspondingly shaped but slightly larger hole 25 in the contact carrier. This arrangement drivingly connects the contacts i9 with the carrier I9 but leaves them free to adjust themselves to the stationary contacts. To reduce friction, each Contact IS has; a small pad 26 embossed therein and riding on the base to hold the body of said contact off the base.

As explained hereinbefore the contact carrier is constrained to edgewise movement in a plane parallel to the base and such movement is imparted thereto from the sliding pitman I2 through a connection 21. This connection comprises a tongue 27 extending from the adjacent edge of the pitman and received in a correspondingly shaped though slightly larger hole 2l" in the contact carrier; and it is to be observed that the location of this connection is forward, in the switch closing direction, of the control portions 2I of the contacts I8 and centrally spaced between them so that the switch closing force is applied to the movable contacts by arrangement similar to the well known wife tree. This allows the movable contacts to adjust themselves to the stationary contacts and assures balanced contact pressure and good electrical connection between contacts.

A coil spring surrounding what may be considered the stem portion of the pitman and confined between the inner wall of the shell 8 adjacent to the hole I3 and a shoulder 29 at the base of the pitman stem portion yieldingly urges the pitman and contact carrier in the switch closing direction.

The manner in which the pitman is retracted against the force of its spring to open the switch is one of the chief features of this invention, and by the novel mechanism employed for this purpose one of the most important objects of the invention is realized, namely the production of a large linear switch opening movement from a small angular motion of the actuator. The actuator in the embodiment of the invention illustrated is the control shaft 39 of a variable resistor indicated generally by the numeral 3i and upon which the switch is mounted. Actually, the shell e provides a housing common to the switch and the resistor since the base of the switch closes one end of the shell and the base 32 of the resistor closes its other end.

At the bacl; of the variable resistor inside this common housing a stamping 33 is secured to the inner end of the shaft 30. Two lugs 34 and 35 project rearwardly from this stamping to travel in separate arcuate orbits concentric to the axis of the shaft. The orbit of the lug 35 which is spaced farthest from the axis of the shaft 30 passes through the indentation I5 in the side wall of the shell 3 so that the lug 35 will collide with the opposite sides of the indentation to limit rotation of the actuator to something slightly less than 360 The other lug 34 coacts with a generally V-shaped cam 36 on the pitman to retract the pitman during rotation of the actuator in a counterclockwise direction as viewed in Figures 2, 3, 4 and 6 and thereby open the switch.

As best illustrated in Figure 6 the arrangement is such that a relatively small angular motion of the actuator, indicated by the angle A, is enough to fully retract the pitman; and to translate this small angular movement of the actuator into linear movement of the pitman the cam 3B has its edge 3?, with which the lug 34 collides, disposed at a relatively steep angle across the orbit of the lug 34.

As will be appreciated the small range of angular movement of the actuator during which the lug 34 rides up the inclined cam edge 31 to retract the pitman takes place just before counterclockwise rotation of the actuator is arrested by the collision of the lug 35 with the adjacent side of the indentation I5.

Slightly before switch opening rotation of the actuator is arrested the lug 34 snaps over the apex 38 of the cam and rides a slight distance down its opposite side 39 coming to rest in the position shown in Figure 2.

It will be evident that as the lug 34 rides over the apex or hump 38 an involuntary snap action occurs. Also, during switch closing movement of the actuator, i. e. during the very rst few degrees of clockwise rotation, the cam 36 rides up the incline 39 and as it crosses the apex 38 the same involuntary snap action takes place. In fact, in this case the rotation of the actuator generally is so rapid at this instant that for ali intents and purposes the lug 34 moves clear of the cam before the spring can act to snap the switch closed.

Attention is directed to the fact that the pit man i2 and its cam 3S are formed as a simple inexpensive stamping and that to assure a good driving connection between the lug et and the cam, the adjacent edge of the pitman is notched as at d@ to accommodate the lug and allow the same to straddle the cam.

The modified embodiment of the invention illustrated in Figures '7, 8 and 9 in its general organization is the same as that described. The difference lies chiefly in the specific design of the pitman, the arrangement of the contacts and the fact that the switch is housed in a casing separate from that which contains the variable resistor. Thus, the casing for the switch comprises a cylindrical stamping di closed at one end by the base 'l' of the switch and at its op posite end by the back i2 of the housing [i3 in which the variable resistor is located, the switch casing being mounted upon the wall d2.

The driving connection between the actuator lug 34 which, of course, operates within the resistor housing 43, and the pitman is established by projecting the flat medial portion 44 of the pitman through an elongated hole it in the wall 42. The nat medial portion liti has two side edges both parallel with the longitudinal axis of the stem of the pitman and one of these side edges is inside the resistor housing d3. A flange it extending laterally from this side edge substantially perpendicular to the plane of the medial portion and the stem provides the cam 3%' in the path of the driving lug 34 so that the arcuate movement of the lug retracts the pitman against the force of its spring in the same manner as hereinbefore described.

The pitman in this modied embodiment of the invention has been designed to give the same greater stability and accordingly its flat medial portion 4d has a ange 41 extending laterally from its side edge opposite the flange it, and substantially perpendicular to the plane of the medial portion and the stem. This ange 4l is bifurcated to provide two relatively widely spaced arms t parallel to the longitudinal axis of the stem and substantially equispaced from and at opposite sides of the plane of the medial portion and stem. These arms pass through holes i9 in the side of the casing 4l at opposite sides of its indentation l5'. With this construction the pitman has a three point support which gives it good stability especially against twisting about its longitudinal axis.

To facilitate the assembly of the switch, the pitman, as stamped and formed, has an extension 5i) joined to its stem by a frangible connection 5l. This extension affords means by which the pitman may be grasped and pulled down through the hole It during assembly of the switch to enable the extremities of the arms i8 to be brought down into alignment with their respective holes i9, it being understood that the contact carrier I9 is of a size to allow the additional travel of the movable contact assembly necessary to this operation. After assembly the extension 5c is broken off.

The only other significant distinction between the two embodiments of the invention illustrated resides in the specific arrangement of the contacts. In the modified embodiment of the switch (Figures '7, 8 and 9) these contacts are symmetrically arranged at opposite sides of the median plane which includes the axis of the pitman. This allows a more compact construction.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention provides a switch especially well adapted for use in radio and television apparatus since it attains maximum switch opening and closing movement from a relatively small angular movement of its rotary actuator, and since it achieves all of the other requirements of a switch of this character with a simple inexpensive construction.

What we claim as our invention is:

l. In an electric switch having a nat base defining an end wall or a substantially cylindrical housing, a movable contact carrier constrained to movement across the flat base and cooperating contacts on the base and movable contact carrier, mechanism ior translating a small angular movement of a rotatable actuator turning upon an axis perpendicular to the base and substantially concentric with the housing into a relatively large linear switch opening and closing movement of the movable contact carrier, comprising: a pitman constrained to linear movement across and parallel to the base; a driving connection between the pitman and the carrier; a spring imposing an endwise thrust upon the pitman and urging the same in one direction; a rotatable actuator constrained to rotation about an axis perpendicular to the base and substantially concentric with the housing; a driving abutment on the actuator movable in an arcuate orbit by rotation of the actuator; and an abutment on the pitman lying in the path or" the driving abutment as the latter moves along its arcuate orbit, the contacting surfaces of said abutments being so disposed that during a small part of the permitted rotation of the actuator in one direction they have transient camming engagement to retract the pitman against the force of its spring.

2. In an electric switch having a cylindrical housing, one end wall of which is formed by a ilat base, a movable contact carrier constrained to movement across the flat b-ase and cooperating contacts on the base and movable contact carrier, mechanism for translating ya small angular movement of a rotatable actuator turning upon an axis perpendicular to the base and substantially concentric with the housing into a nrelatively large linear switch opening and closing movement of the movable contact carrier, comprising: a pitman constrained to linear movement across and parallel to the base; a driving connection between the pitman and the carrier; a spring imposing an endwise thrust upon the pitman and urging the same in one direction; ya rotatable actuator constrained to rotation about an axis perpendicular to the base and substantially concentric with the housing; a driving lug on the actuator movable in lan arcuate orbit by rotation of the actuator; and an abutment on the pitman having an inclined cam surface extending across the orbit of the driving lug when the pitman is in its position to which it is urged by the spring to be transiently engaged by the driving lug during a small angular rotation of the actuator in one direction, which engagement forces the pitman in a direction opposed to the thrust of the spring.

3. In an electric switch, the structure set forth in claim 2 further characterized by the fact that the abutment on the pitman has a second op.-

rpositely inclined cam surface and a substantially pointed apex joining the two cam surfaces and across which the driving lug moves in its travel.

4. In an electric switch: a casing housing the switch and including a cylindrical shell; a pitman having opposite end portions slidably received in substantially diametrically opposite holes in the shell; a spring acting on the pitman and biasing the same linearly in one direction; va rotatable control shaft entering the ycasing and substantially coaxial with the cylindrical shell; a driving lug fixedly connected to the control shaft inside the casing and constrained to travel in an arcuate orbit lying adjacent to the pitman; an abutment on the pitman having an inclined surface intersecting the orbit of the driving lug and engageable thereby upon rotation of the control shaft in one direction to translate rotation of the control shaft into linear movement of the pitman in a direction opposed to the bias of the spring; a movable contact carrier within the casing; and a driving connection between the pitman and the Contact carrier.

5. In an electric switch: a casing housing the switch and including a cylindrical shell; a pitman having opposite end portions slidably received in substantially diametrically opposite holes in the shell; a spring acting on the pitman and biasing the same linearly in one direction; a rotatable control shaft entering the casing and substantially coaxial with the cylindrical shell; a driving lug xedly connected to the control shaft inside the casing and constrained to travel in an arcuate orbit lying adjacent to the pitman; an abutment on the pitman having a surface intersecting the orbit of the driving lug and engageable thereby upon rotation of the control shaft in one direction to translate rotation of the control shaft into linear movement of the pitman in a -direction opposed to the bias of the spring; lan insulated switch base closing the cylindrical shell at the other side of the pitman from the orbit of the driving lug, Iand having its inner face lying in a plane parallel to the longitudinal axis of the pitman; a movable contact carrier between the switch base `and the pitman; a driving connection between the pitman and the movable contact carrier through which reciprocaticn of the pitman moves the carrier across the switch base; and cooperating contacts on the carrier and the switch base.

6. In an electric switch, the combination set forth in claim 5 further characterized by the provision of guides mounted on the switch base and having guiding engagement with one side of the movable contact carrier; and a guide surface on the pitman engaging the other side of the movable contact carrier, so that said guides and the guide surface on the pitman coact to constrain the movable contact carrier to movement across and parallel to the inner face of the switch base.

'7. In an electric switch having a switch base with a substantially flat face and dening one end of a housing having a substantially cylindrin cal wall, and spaced stationary contacts mounted on said switch base: a movable contact carrier constrained to movement within the housing across and parallel to said face of the switch base; a driving member; means mounting and constraining the driving member to reciprocation across the switch base with its longitudinal axis parallel to said face of the base and lying in a plane substantially centered between the stationary contacts, the movable contact carrier being between the driving member and the switch base; driving connection between the driving member and the movable contact carrier so that the movable contact carrier partakes of the movement of the driving member; and spaced contacts on the movable carrier arranged in balance at opposite sides of the plane along which the driving member moves, said contacts being cooperable with the stationary contacts.

8. 'In an electric switch, mechanism for imparting switch opening and closing movement to its movable contact carrier characterized by: a sliding pitman constrained to linear movement along its longitudinal axis; a spring acting on the pitman and urging it in one direction; a rotatable 'actuator mounted to turn through the major portion of a complete rotation on an axis Contiguous and perpendicular to the longitudinal axis of the pitman; a driving lug on the actuator movable along an arcuate orbit by rotation of the actuator; and an abutment on the pitman having an inclined surface intersecting the orbit of the driving lug to be transiently engaged by said driving lug in a portion of its orbit to move the pitman against the bias of its spring.

9. In an electric switch, the mechanism set forth in claim 8, but wherein the pitman is a sheet metal stamping and the abutment thereon is in the form or a iiange extending laterally from one edge o the stamping.

l0. In an electric switch, the mechanism set forth in claim 8, wherein the pitman is a sheet metal stamping having-a nat medial portion with two substantially1 parallel side edges, a narrow stem projecting from the medial portion with its longitudinal axis substantially Vparallel with said two do edges, said stem beingcoplanar-with the portion, a flange extending laterally from one side edge oi the medial portion, one edge of said ange being shaped to provide the abutment on the pitman which is engaged by the driving lug of the actuator, another ange extending lateraliy from the other side edge of the medial portion, said last named iiange being bifurcated to 'provide two spaced arms both of Awhich are parallel with the longitudinal axis of the stern, said two arms dening the extremity of the p`itman opposite that provided by the stem.

l1. In an electric switch, the combination with a casing having a substantiallycylindrical side wall closed at one end by an insulated contact carrying base, "a movable Contact carrier overlying the base within the casing, and cooperating contacts on the base and the movable contact carrier, of means for imparting contact opening and closing movement to the carrier, comprising: a pitman having an elongated stem slidably received in a hole in the side wall of the casing; a pair of spaced arms on the end of the pitman opposite said stem slidably received in holes in theside wall of the casing whereby said pitman is restrained to reciprocating motion at `three points; a driving connection between the pitman and the movable contact carrier; a spring acting upon the pitman to yieldingly urge the same in one direction; and a cam on the medial portion ofthe pitman by which an actuator mayimpart motion to the pitman in opposition to its spring.

12. As an article of manufacture, a pitman for imparting switch opening and closing motion to the movable contact carrier of an electric'switch, comprising: a sheet metal stamping having a flat medial portion with two parallel side edges;

a narrow elongated stem projecting from the at medial portion with its longitudinal axis sub stantially parallel with said two side edges, the entire stem being coplanar with said medial portion; a flange extending laterally from one of said two side edges of the medial portion and lying in a plane substantially perpendicular to that of the medial portion and the stem, said flange being shaped to provide two oppositely inclined cam surfaces joined to define an apex pointing in the direction opposite that toward which the stem projects; a second ange extending laterally from the other side edge of the medial portion and also lying in a plane substantially perpendicular to the medial portion and the stem, said second flange being bifurcated to provide two spaced parallel arms which project in the direction opposite that toward which the stem projects so as to provide the extremity of the pitman opposite that provided by the stem, said spaced parallel arms being equispaced from and lying at opposite sides of the plane of the at medial portion and the stem, and said arms together with the stem providing three parallel guide portions by which the pitman may be slidably mounted.

13. The pitman structure of claim 12 further characterized by the provision of an extension on the end of the stem joined thereto by a frangible connection whereby said extension may be readily broken off after the pitman has been assembled with the switch.

14. In an electric switch having a housing and stationary contacts exposed at the at inner face of a base which provides an end Wall of the housing: a driving member inside the housing; means mounting and constraining the driving member to reciprocation along a path parallel to and spaced from said face of the base; a flat movable contact carrier conned between the driving member and said face of the base and edgewise reciprocable to carry a movable contactor to and from bridging engagement with the stationary contacts; a connection between the driving member and the movable contact carrier for imparting motion of the driving member in one direction of reciprocation to the movable contact carrier to move the latter away from its position holding the contact in bridging engagement with the stationary contacts; means yieldingly biasing the movable contact carrier in the other direction; a rotatable actuator accessible at the exterior of the housing and extending into the housing, said actuator being rotatable through at least the major portion of a full turn on an axis perpendicular to said flat face of the base; and cooperating cam means on the driving member and the actuator transiently engageable during a small portion of the rotation of the actuator to impel the driving member in a direction to carry the movable contact carrier away from its position at which its contactor is in bridging engagement with the stationary contacts.

WILKIE L. BUSH. ARTHUR M. DAILY.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 675,294 Pieper et al May 28, 1901 1,224,119 Sutherland Apr. 24, 1917 1,748,298 May Feb. 25, 1930 1,880,676 Beck Oct. 4, 1932 2,366,474 Bentley Jan. 2, 1945 

